Electron tube grid structure



June 7, 1949. B. ZETKA 2,472,767

ELECTRON TUBE GRID STRUCTURE Filed March 19, 1947 INVENTOR. Jame viz [7'- Zeifi'fl Patented June 7, .1949

miner nnnnnmnonmn 'enmis mmmnn Joseph-i. rtzeikeeaolirt mz ent.Jnessi ncae .SylxziLniE-Jllecitric Pmductsilncz, a; corporation .IdfTMassachusetts tiae neetiemmerenm;mitesaennuearssaza Tl BfClaims. (01ZZ250;-T-27.5) N v 1 I I .ififIhiS: invention @relates to. electronitubes, nnore and aimethod of manufacturing. embodyingrthe paparticularlylto. d.isc+typeemeshrgridscefor userin ieat uresilot;th sdnuention, I ate-suchttubes tand.tortheemethod ofima-kingithem. tE1g...J.- issa-nainahwiewtof a grid.frame with-l the I .a. Inacertainofth-e e'lectron -tubes-ii-mwhioh 'azdiscrid meshlemheddedithereln. v I hmypermeshtgrid. is usedeiconsiderablediffioulitfihas reamedge-viemuf theedevice illustrated been encountered heretotoreein mahingrsais ac- M n-. I a-.-t r .icentactibetweemthe wiresof the grid: and :E e. 3 is as tion hgv ewe fi the; da he er d thegridirame. ameerand a Jig: usednnepress ngtthem together. aFor exampleainesomeivelocity modulatemrtubes -F.1g-- 4t 18 a -side elevation; 'lpartltmn se tmrm9f standtotheri highntrequencymdisceseal-.-tuhes;-. itfitwwfi;10 a p p t s e d tafoundthatihighpdwen-outputifromwtheitubeicould i m d rld frame. cxebe obtainedonly; itieacheindividua-l rwreazatathe 8 a a frasm nta y l f fln' o periphery of the grid in the, structnreawaseindiesnd i a e s win e dr vidually weldechtorthe grid frame. This method e fl odlment.ctthedmmtypw i of making grids is necessarily difficult and withzzifi r tediiriithedr wi e omh snan very smallcgrichiwiresrhavingirdiameters of the eifi c tmdetmadeeof. a: c1rcu .r p1e 1etoi-.'.w1re rmesh order.of of an inch it becomes vintua lly gr;d temounted on an.iannularigrldtfirame,2. 14111 a ipogs-ible to accomplish it .1.aparticulanapplmatlonefon.whichmuch astrueture Furthermore, after the Wires are Welded in this =*f gnfliimeshewas Y n sten manner? it 'isrrecessary to clean them. This is?! oloo-lzewchim diameterriwhller'thewelectmde normally accomplished with? the aid of;: an-..acid 8-1 1??? og'e-grid flamecwas efsrmedrfmmewprer iiabathr-orrb firing in hydrogen. Cleaning! with w e i it'acid 151-11183 113 objectionabl e.eparticularlintomwire hee d-"fn me may biz-shaped.in-anymanner are: smalhdiameter since the-tacid disseives-epart suitable "-i? 15-F p fi j 15 e ilof the wire and the consequent dfidllctiollfiflfiiamwii-ZQ 'P i ete'r deleteriously affects the electrical characterf 3 and 4 to Promote llgldlty, a flat area istics of the tube produced with such grid. The 5 posltwned between the shouldfarsi adapted for method f cleaning by firin in hydrogen is also sealing the sections of glass tubing which make objectionable because it makes the grid wires part of the glass envelqpe tube f an brittle. Furthermore, inasmuch as the cleaning Inner annular flat area 6 m Whlch the grld Wire operation is usually incomplete, a longer exhaust is embeddedschedule is usually required for outgassing the The shape and size of the g g 'g tubes at a further cost in time which may be i be chosfm to conform Wlth he es re added to the Original slow method of welding electrlcal properties of the tube. Furthermore,

. the jigs used in pressing the grid wires into the Aeicordmgly Object of thls mvemimn Is to 3 frame may, as will be hereinafter explained, aid provide a substitute method of assembling mesh in giving the grid its desired shape type grids which is not subject to these disadvantages. A further object of the invention is to improve the mechanical and electrical bond be- 40 tween the mesh grid and its frame. Still another object of this invention is to improve the grid structure and the method of making it.

In accordance with my invention, these and other advantages which are incidental to its application, can be obtained by embedding the wires of the grid mesh in the inner periphery of the grid frame. This can be accomplished by holding the grid wire and the frame together in a ji and subjecting them to the application of A circular section of the desired grid mesh is then h pressure. This causes the metal on the placed over the circular opening of the disc with frame to flow about the relatively hard grid wires its edge overlying a substantial area of the immeand produces an excellent bond between the two. diately adjacent grid frame. The two sections In the accompanying drawings which illustrate 1 and 8 of the jig are then brought together under the preferred forms of the improved structure considerable pressure. Due to the shape of the frame and mesh is clearly illustrated in Fig. 3 of the drawing. In the embodiments there shown, the jig is composed of two sections 1 and 8 which are formed in such manner as to conform with the shape of the grid support shown in the remaining figures of the drawing. It could, naturally, conform to other desired shapes.

When using a jig of this type, a shaped annular disc provided with an opening of the proper size, is placed on the surface 9 of section I of the jig A preferred method of assembling the grid with its inner circular opening abutting edge I5.

When pressure is brought to bear, this edge forms a circular groove IS in the grid frame and causes the end v of the wires to be turned downward and become embedded therein.

When the pressure is released and the jig removed, the grid frame and grid mesh wire form a single unitary structure in which the periphery of the grid mesh 1 cannot move in any direction with respect to the grid frame and the shape of the curved central portion is precisely maintained. Furthermore, the process of joining the two parts is purely mechanical, no chemical action of any kind is involved and no subsequent treatment is necessary. There is, therefore, no corrosion or exidation of the type normally encountered when using the prior art welding technique.

It is naturally understandable that the shape of the jig could be such that it could also simultaneously form the grid frame from a fiat annular disc as well as to embed the mesh l into 4 the grid frame. The method illustrated is merely a preferred one in which the frame is previously formed and the wire mesh embedding operation is carried out subsequently.

The pressure used in this operation will also naturally vary within wide limits dependin upon many variables including the Wire size, materials used, the depth of embedding desired and the shape of the finished grid. It has been found,

for example, that a pressure of 2 tons is adequate for making a grid of the design shown in the drawing when the grid frame is made of copper and the Wire is 0.0012 inch tungsten.

A grid and grid frame embodying the features of this invention are shown incorporated in an electron tube in Fig. 4. The disc 2 is sealed between sections of the tubular envelope holding the mesh l in the center of the tube where it acts as a control element for an axial electron beam.

While the above description and the drawings submitted herewith disclose preferred and practical embodiments of the grid mesh and frame assembly of this invention, it will be understood by those skilled in the art, that the specific detail of construction and arrangement of parts a; shown and described are by way of illustratiom and are not to be construed as limiting the scope of the invention.

What I claim is:

1. A mesh grid for an electron tube comprising a mesh of relatively hard wires and an annular grid frame of softer metal, the wires having their ends embedded adjacent the inner edge of the annular grid frame.

2. A grid and grid frame assembly for an electron tube comprising a disc-like mesh of wires having its circular periphery embedded adjacent the inner circumference of an annular disc, the ends of said grid wires being embedded in a circular groove in said disc.

3. In an electron tube having an evacuated tubular envelope, a central electrode comprising a mesh of wires with its periphery embedded in an annular disc adjacent the inner circumference, said disc projecting through said envelope and being sealed thereto with its outer periphery outside said envelope.

' JOSEPH B. ZETKA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,025,224 Dodge Dec. 24, 1935 2,261,154 Hansen et al Nov. 4, 1941 2,402,119 Beggs June 18, 1946 2,414,785 Harrison et a1 Jan. 21, 1947 

